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CAIB meeting
Members of the Columbia Accident Investigation Board (CAIB) during one of their meetings. Their report formed the basis of the decision to retire the Space Shuttle. (credit: Rick Stiles)

The decision to retire the Space Shuttle


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In a few days Space Shuttle Atlantis will touch down on Earth and close a chapter of American human space flight. Thus it is a good time to reconstruct how the decision was made to retire the Space Shuttle.

One key conclusion reached by Group IV during the course of its work was that NASA leadership changed the planned retirement date for the shuttle several times over the years, but had never done so based primarily upon an actual assessment of the shuttle’s physical status.

The beginning of the end for the Space Shuttle program came with the destruction of the Columbia over the American southwest in early February 2003. Immediately after the accident, NASA administrator Sean O’Keefe activated the Columbia Accident Investigation Board, or CAIB. Very early in the investigation one common topic of discussion among CAIB members and staff was whether the shuttle was too dangerous to continue flying, and whether the CAIB should recommend its immediate retirement. There were some members of the CAIB staff—and perhaps some of the original Board members themselves—who believed that the shuttle should never fly again. But the CAIB membership was expanded twice, and as the technical investigation progressed and even before the CAIB turned to issues of policy and budget, this view subsided. CAIB members eventually began to accept the view that the shuttle could continue flying, albeit with new restrictions, and a better awareness of the risk associated with every flight.

Nearly two months into the investigation the CAIB established “Group IV,” which was tasked with investigating organization and policy issues associated with the accident. Group IV was headed by Board member John Logsdon, and he and his small team of investigators—complemented by CAIB board member inputs—began looking at how organization, policy, and budget decisions made in the years before the accident may have served as contributing factors. The group looked at the original decision in the early 1970s to build a particular shuttle design, as well as the programmatic decisions since then. But most of the relevant decisions essentially stemmed from the mid-1990s.

One key conclusion reached by Group IV during the course of its work was that NASA leadership changed the planned retirement date for the shuttle several times over the years, but had never done so based primarily upon an actual assessment of the shuttle’s physical status. The retirement dates had shifted based upon the status of a replacement for the shuttle. For example, when the Lockheed Martin X-33, which was planned to lead to a shuttle successor, was canceled in 2001, NASA did not initiate a follow-on program. Instead, NASA officials essentially decided to move the retirement date of the shuttle from 2012 to 2020, and in 2002 commissioned a study to identify the long-term requirements to make this possible.

As the CAIB investigation moved into its report writing stage in summer 2003, the Board formulated a recommendation calling for NASA to “recertify” the shuttle by 2010. That recommendation was included in the CAIB’s final report, issued in September 2003:

The Board makes the following recommendation regarding recertification:

R9.2-1 Prior to operating the Shuttle beyond 2010, develop and conduct a vehicle recertification at the material, component, subsystem, and system levels. Recertification requirements should be included in the Service Life Extension Program.

The CAIB justified this recommendation in the following terms:

Recertification

Recertification is a process to ensure flight safety when a vehicle’s actual utilization exceeds its original design life; such a baseline examination is essential to certify that vehicle for continued use, in the case of the Shuttle to 2020 and possibly beyond. This report addresses recertification as a mid-term issue.

Measured by their 20 or more missions per Orbiter, the Shuttle fleet is young, but by chronological age – 10 to 20 years each – it is old. The Board’s discovery of mass loss in RCC [reinforced carbon carbon] panels, the deferral of investigation into signs of metal corrosion, and the deferral of upgrades all strongly suggest that a policy is needed requiring a complete recertification of the Space Shuttle. This recertification must be rigorous and comprehensive at every level (i.e., material, component, subsystem, and system); the higher the level, the more critical the integration of lower-level components. A post-Challenger, 10-year review was conducted, but it lacked this kind of rigor, comprehensiveness and, most importantly, integration at the subsystem and system levels.

Aviation industry standards offer ample measurable criteria for gauging specific aging characteristics, such as stress and corrosion. The Shuttle Program, by contrast, lacks a closed-loop feedback system and consequently does not take full advantage of all available data to adjust its certification process and maintenance practices. Data sources can include experience with material and component failures, non-conformances (deviations from original specifications) discovered during Orbiter Maintenance Down Periods, Analytical Condition Inspections, and Aging Aircraft studies. Several of the recommendations in this report constitute the basis for a recertification program (such as the call for nondestructive evaluation of RCC components). Chapters 3 and 4 cite instances of waivers and certification of components for flight based on analysis rather than testing. The recertification program should correct all those deficiencies.

Finally, recertification is but one aspect of a Service Life Extension Program that is essential if the Shuttle is to continue operating for another 10 to 20 years. While NASA has such a program, it is in its infancy and needs to be pursued with vigor. The Service Life Extension Program goes beyond the Shuttle itself and addresses critical associated components in equipment, infrastructure, and other areas.

There are two important points to understand about the CAIB’s recommendation: the date was not arbitrary, and the recommendation was more about policy than about the physical condition of the orbiters.

Notably, the CAIB did not explicitly recommend the retirement of the shuttle by 2010. However, at least some Board members expected recertification to have the same effect, and some of them acknowledged that NASA would struggle with recertifying the shuttle.

The 2010 date was not selected based upon an expectation of the material condition of the orbiters seven years after the CAIB report was released. It was selected because that was when Board members believed that construction of the International Space Station would be complete. This had not been an automatic early assumption among Board members. Only a few of the Board members or CAIB professional staff had experience with the American space program. Most of the Board members and staff instead came from military and commercial aviation backgrounds. They had little awareness of the International Space Station or its importance to American national and international policy.

At the time, Board members believed that the shuttle would resume flying in either 2004 or early 2005 and could potentially complete space station construction by 2008 or 2009 at the latest. Thus, by selecting the 2010 date, the CAIB was acknowledging the importance of the shuttle in accomplishing what had become the primary goal of the American human spaceflight program: construction of the International Space Station. Presumably, ISS construction could be completed and ISS could be serviced for up to a year longer before the recertification requirement. In reality, the shuttle did not resume flying until 2005, and then suffered problems that prevented another launch until 2006.

The second key aspect of the CAIB’s recommendation was the act of recertification itself. Notably, the CAIB did not explicitly recommend the retirement of the shuttle by 2010. However, at least some Board members expected recertification to have the same effect, and some of them acknowledged that NASA would struggle with recertifying the shuttle, at least according to the commonly accepted practice of recertification of military aircraft fleets. The CAIB recommended recertification as a forcing function intended to make the nation’s political leadership, as well as NASA’s leadership, break the cycle of extending the shuttle’s lifetime without a formal, and intense, process of evaluation.

In January 2004 the Bush administration issued the Vision for Space Exploration. The Vision had four main policy points. The first dealt exclusively with the Space Shuttle:

Space Shuttle

  • Return the Space Shuttle to flight as soon as practical, based on the recommendations of the Columbia Accident Investigation Board;
  • Focus use of the Space Shuttle to complete assembly of the International Space Station; and
  • Retire the Space Shuttle as soon as assembly of the International Space Station is completed, planned for the end of this decade.

Soon after, NASA established 2010 as the retirement date for the shuttle. It is unclear what the Bush administration’s rationale was for this decision. It was likely influenced by the CAIB recommendation. It is also possible that the administration sought shuttle retirement for its own reasons. Nevertheless, shuttle retirement was required to free up money to implement the other aspects of the Vision for Space Exploration. Notably, for the first time the government announced plans for retiring a space vehicle without a replacement in the works, a reversal of past practice.

However, by not continuing with Constellation, and not having begun a parallel commercial-based path years earlier, the government had made a de facto choice regarding an interim replacement—the Russian Soyuz.


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